Subpicosecond study of excitons in a phenylenevinylene conjugated polymer: exciton–exciton interactions and infrared photoinduced absorption features

We present a study of the fundamental photoexcitations in a phenylenevinylene conjugated polymer from the visible to the mid-infrared (IR) using polarized subpicosecond transient absorption (TA) spectroscopy. From 0.5 to roughly 1.3 eV we find that features due to singlet intrachain excitons dominate the photoinduced absorption. Two peaks are apparent in the spectrum: one near 0.5 eV and the other at ∼1.1 eV. In the regime of high excitation densities (>1019 cm−3), we find evidence of exciton–exciton interactions leading to exciton hopping between different chains or segments of the polymer.